Measuring chlorophyll and plant samples, such as leaves of fruit plants is important in determining that the plant has proper conditions (e.g., habitat, nutrients, lighting, etc.) for optimum growth.
It is known to conduct laboratory chemical analysis of plant samples to determine chlorophyll content. Such analysis involves the steps of collecting samples, drying and grinding the samples, performing chemical analysis of the samples and interpreting the results. Chemical analysis, however, is time consuming, expensive and requires professional expertise. In addition, such analysis is usually not available in time to adjust growing conditions (e.g., fertilization) for a current year's crop.
Some efforts have been made to provide portable devices or meters to provide an indication of chlorophyll content in a sample. The SPAD meter (produced by Minolta of Japan) is widely used by growers and researchers throughout the world. The SPAD meter has a cost of about $1,500. The SPAD-502 weighs 225 grams, has a 0.06 cm2 measurement area and calculates an index in SPAD units based on absorbance at 650 nm and 950 nm. The claimed accuracy of the SPAD-502 is +/−1.0 SPAD units.
The Chlorophyll Content Meter-200 (CCM-200, produced by Optiscience) costs about $1,000, weighs 180 grams, has a 0.71 cm2 measurement area and calculates a chlorophyll content index (CCI) based on absorbance measurements at 660 nm and 940 nm. The claimed accuracy of the CCM-200 is +/−1.0 CCI units.
The Chlorophyll Meter-1000 (CM-1000, produced by Spectrum Technology, Inc.) costs $2,500. The CM-1000 weighs 692 grams and calculates an index in CM-1000 units based on reflectance at 700 nm and 840 nm. The recommended sampling distance for the CM-1000 is 28.4 to 183.0 cm with a corresponding sampling scope of 1.10 to 18.8 cm in diameter outlined with the high powered lasers.
Another meter, the CL-01 Chlorophyll Content Meter, weighs 250 grams, can measure leaf samples up to a maximum of 12.7 cm wide and calculates a chlorophyll index based on absorbance at 620 nm and 940 nm.
These conventional meters, however, do not provide high accuracy results. In addition, each of these meters gives an indication of chlorophyll content based on a different index. None of these meters directly gives a chlorophyll content result or a nitrogen content result. Also, none of these meters conveys its results in connection with a real world location, such that a user surveying an entire field of a particular crop could correlate trends in chlorophyll values with particular locations of the samples, among other uses for such information.